The agrochemical industry is continually seeking methods of improving the growth of plants. Chemicals are typically used to control undesirable species, such as insects or vegetation (e.g. weeds or fungi) and to promote plant growth (e.g., by providing nutrients), thereby improving the growth of plants.
Aside from to direct damage caused by external factors such as plant pests, or the lack of nutrients, the growth of a plant is affected, often detrimentally, by the plant's own responses to external environmental stress factors. When subjected to such stress factors plants display a variety of mechanistic responses as protective measures, with a resultant adverse effect on growth, development, and productivity. Significant losses in quality and yield are commonly observed.
Acibenzolar (benzo[1,2,3]thiadiazole-7-carbothioic S-acid), acibenzolar-S-methyl(S-methyl benzo[1,2,3]thiadiazole-7-carbothioate), and probenazole (3-allyloxy-1,2-benzothiazole 1,1-dioxide), are plant activators that are used for controlling fungi and bacteria. Plant activators are substances that protect plants by activating their defence mechanisms against pests or diseases.
Trinexapac ((RS)-4-cyclopropyl(hydroxy)methylene-3,5-dioxocyclohexanecarboxylic acid), its ethyl ester trinexapac-ethyl, prohexadione (3,5-dioxo-4-propionylcyclohexanecarboxylic acid) and triazoles, such as paclobutrazol ((2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-01), tebuconazole ((RS)-1-p-chlorophenyl-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol) and metconazole ((1RS,5RS;1RS,5SR)-5-(4-chlorobenzyl)-2,2-dimethyl-1-(1H-1,2,4-triazol-1-ylmethyl)cyclopentanol) are gibberellic acid synthesis inhibitors. Gibberellic acid is a phytohormone that promotes growth in plants.
Trinexapac-ethyl (TXP) and prohexadione-Ca are used for plant growth regulation in cereals, especially in wheat, and trinexapac-ethyl is also used for the management of growth of warm and cool season turfgrass on golf courses, sod farms, residential lawns and other areas, thereby eliminating the need for frequent mowing and grass clipping. The material is applied by ground sprayers and granule spreaders.
Paclobutrazol (PBZ) is used as a spray on the plant crops of ornamentals and orchards to reduce plant growth and stimulate flowers. It is also used by arborists to reduce shoot growth and has been shown to have additional benefits for trees and shrubs when administered by soil drench or soil injection methods, including improved resistance to drought stress, darker green leaves, protection against some fungal and bacterial pathogens, and enhanced development of fibrous roots. (W. R. Chaney, D. M. Mickey and H. A. Holt; www.pgrsa.org/2005_Proceedings/papers/028.pdf).
Neonicotinoids are used as insecticides applied as a spray and/or seed treatment to protect plant crops from pests. Beside the insecticide effects and beside others, thiamethoxam is used as seed treatment to stimulate the plant growth.
Stobilurins are used as fungicides applied as a spray and/or seed treatment to protect plant crops from disease.
European patent EP 0,220,514 refers to compositions comprising phytohormones and their use in methods for increasing the quantity and quality of fruits or flowers of plants in horticulture or agriculture. International patent application WO 2005/018319 refers to the application of auxins to the roots of plants by drip irrigation or spray application in order to inhibit insect infestation.
There is a need for additional methods for dealing with the environmental stresses experienced by plants in order to increase their tolerance thereto, and to improve the quality and yield of a plant crop subject to those stresses.